1. Field of Invention
This invention relates to a method for fabricating a metallic oxide of high dielectric constant, a metallic oxide of high dielectric constant, a gate insulating film and a semiconductor element.
2. Description of Related Art
Conventionally, Si oxide film has been employed as a gate insulating film of a semiconductor element such as a Si MOSFET, in view of thermal stability and interfacial characteristic. However, with the development of performance and function of a semiconductor element, thinning the Si oxide film is intended. However, it is considered that the thinning of the Si oxide film is limited. Therefore, attention is paid to an insulating film of high dielectric constant substituted for the Si oxide film as the insulating film of high dielectric constant.
In the use of the insulating film of high dielectric constant as the gate insulating film, various properties are required, such as high dielectric constant, low leak current, low defect density and flat interface between the Si substrate and the insulating film without any interface layer.
A conventionally developed insulating film of high dielectric constant has only a polycrystalline structure, so that the large leak current is flowed through the insulating film because the grain boundaries of the insulating film serve as leak current paths. As a result, the conventional insulating film of high dielectric constant can not be employed as the gate insulating film. Also, in the fabrication of the insulating film of high dielectric constant, an interface layer of low dielectric constant and large surface roughness is formed through the reaction between the insulating film deposited and the Si substrate. Thus, the operating performance of the intended Si MOSFET and the like containing the insulating film of high dielectric constant is deteriorated.